This invention relates generally to microwave ovens and more particularly to a microwave oven antenna providing improved cooking uniformity.
As is known in the art, microwave ovens provide an effective way of cooking foods faster than can be achieved with conventional ovens. Microwave ovens include a magnetron for providing microwave radiation or energy and a feed arrangement to couple the radiation to a cooking cavity. In one type of feed arrangement, microwave energy is fed down a waveguide to a coaxial probe which is connected to an antenna in the cooking cavity.
As is also known in the art, a common problem associated with microwave ovens is uneven cooking. More particularly, undesirable hot and cold spots may occur in microwave cooked foods. This uneven cooking is due to, inter alia, a non-uniform distribution or pattern of the microwave energy within the cooking cavity.
One method known in the art for improving the uniformity of microwave cooking is to use a directive antenna. Such an antenna is designed to direct the microwave energy to form a desired pattern. However, the load (i.e. the food product) also impacts the microwave radiation pattern. Thus, unless only one type of food product is to be cooked in the microwave oven, the use of a directive antenna may not provide consistent cooking uniformity.
Another method for improving the uniformity of microwave cooking is to randomize the microwave pattern within the cooking cavity with a mode stirrer device, such as a rotating paddle. Although providing some improvement, mode stirrers have only been marginally effective. Another approach has been to rotate the food product within the cooking cavity, for example with a turntable device. In this way, what would otherwise be cold spots in the food are continuously moved to expose such portions to the microwave energy. Alternatively, the randomness of the radiation pattern can be increased by rotating the microwave antenna.